Dry-etch for silicon-and-nitrogen-containing films

ABSTRACT

A method of etching exposed silicon-and-nitrogen-containing material on patterned heterogeneous structures is described and includes a remote plasma etch formed from a fluorine-containing precursor and an oxygen-containing precursor. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the exposed regions of silicon-and-nitrogen-containing material. The plasmas effluents react with the patterned heterogeneous structures to selectively remove silicon-and-nitrogen-containing material from the exposed silicon-and-nitrogen-containing material regions while very slowly removing other exposed materials. The silicon-and-nitrogen-containing material selectivity results partly from the presence of an ion suppression element positioned between the remote plasma and the substrate processing region. The ion suppression element reduces or substantially eliminates the number of ionically-charged species that reach the substrate. The methods may be used to selectively remove silicon-and-nitrogen-containing material at more than twenty times the rate of silicon oxide.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/448,541 filed Apr. 17, 2012 titled “DRY-ETCH FORSILICON-AND-NITROGEN-CONTAINING FILMS,” which application claims thebenefit of U.S. Prov. Pat. App. No. 61/525,067 filed Aug. 18, 2011, andtitled “DRY-ETCH FOR SILICON-AND-NITROGEN-CONTAINING FILMS,” which isincorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess which etches one material faster than another helping e.g. apattern transfer process proceed. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits and processes, etch processes have been developedwith a selectivity towards a variety of materials. However, there arefew options for selectively etching silicon nitride faster than silicon.

Dry etch processes are often desirable for selectively removing materialfrom semiconductor substrates. The desirability stems from the abilityto gently remove material from miniature structures with minimalphysical disturbance. Dry etch processes also allow the etch rate to beabruptly stopped by removing the gas phase reagents. Some dry-etchprocesses involve the exposure of a substrate to remote plasmaby-products formed from one or more precursors. For example, remoteplasma excitation of ammonia and nitrogen trifluoride enables siliconoxide to be selectively removed from a patterned substrate when theplasma effluents are flowed into the substrate processing region. Remoteplasma etch processes have also been developed to remove siliconnitride, however, the silicon nitride selectivity of these etchprocesses (relative to silicon) has been limited.

Methods are needed to improve silicon nitride selectively relatively tosilicon for dry etch processes.

BRIEF SUMMARY OF THE INVENTION

A method of etching exposed silicon-and-nitrogen-containing material onpatterned heterogeneous structures is described and includes a remoteplasma etch formed from a fluorine-containing precursor and anoxygen-containing precursor. Plasma effluents from the remote plasma areflowed into a substrate processing region where the plasma effluentsreact with the exposed regions of silicon-and-nitrogen-containingmaterial. The plasmas effluents react with the patterned heterogeneousstructures to selectively remove silicon-and-nitrogen-containingmaterial from the exposed silicon-and-nitrogen-containing materialregions while very slowly removing other exposed materials. Thesilicon-and-nitrogen-containing material selectivity results partly fromthe presence of an ion suppression element positioned between the remoteplasma and the substrate processing region. The ion suppression elementreduces or substantially eliminates the number of ionically-chargedspecies that reach the substrate. The methods may be used to selectivelyremove silicon-and-nitrogen-containing material at more than ten timesthe removal rate of silicon.

Embodiments of the invention include methods of etching a patternedsubstrate in a substrate processing region of a substrate processingchamber. The patterned substrate has an exposedsilicon-and-nitrogen-containing region. The methods include flowing eachof a fluorine-containing precursor and an oxygen-containing precursorinto a remote plasma region fluidly coupled to the substrate processingregion while forming a plasma in the plasma region to produce plasmaeffluents. The methods further include etching the exposedsilicon-and-nitrogen-containing region by flowing the plasma effluentsinto the substrate processing region.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the disclosed embodiments. The features andadvantages of the disclosed embodiments may be realized and attained bymeans of the instrumentalities, combinations, and methods described inthe specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedembodiments may be realized by reference to the remaining portions ofthe specification and the drawings.

FIG. 1 is a flow chart of a silicon nitride selective etch processaccording to disclosed embodiments.

FIG. 2A shows a substrate processing chamber according to embodiments ofthe invention.

FIG. 2B shows a showerhead of a substrate processing chamber accordingto embodiments of the invention.

FIG. 3 shows a substrate processing system according to embodiments ofthe invention.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION OF THE INVENTION

A method of etching exposed silicon-and-nitrogen-containing material onpatterned heterogeneous structures is described and includes a remoteplasma etch formed from a fluorine-containing precursor and anoxygen-containing precursor. Plasma effluents from the remote plasma areflowed into a substrate processing region where the plasma effluentsreact with the exposed regions of silicon-and-nitrogen-containingmaterial. The plasmas effluents react with the patterned heterogeneousstructures to selectively remove silicon-and-nitrogen-containingmaterial from the exposed silicon-and-nitrogen-containing materialregions while very slowly removing other exposed materials. Thesilicon-and-nitrogen-containing material selectivity results partly fromthe presence of an ion suppression element positioned between the remoteplasma and the substrate processing region. The ion suppression elementreduces or substantially eliminates the number of ionically-chargedspecies that reach the substrate. The methods may be used to selectivelyremove silicon-and-nitrogen-containing material at more than ten timesthe removal rate of silicon.

The ion suppression element functions to reduce or eliminate ionicallycharged species traveling from the plasma generation region to thesubstrate. Uncharged neutral and radical species may pass through theopenings in the ion suppressor to react at the substrate. It should benoted that complete elimination of ionically charged species in thereaction region surrounding the substrate is not always the desiredgoal. In many instances, ionic species are required to reach thesubstrate in order to perform the etch and/or deposition process. Inthese instances, the ion suppressor helps control the concentration ofionic species in the reaction region at a level that assists theprocess.

In accordance with some embodiments of the invention, an ion suppressoras described in the exemplary equipment section may be used to provideradical and/or neutral species for selectively etching substrates. Inone embodiment, for example, an ion suppressor is used to providefluorine and oxygen containing plasma effluents to selectively etchsilicon-and-nitrogen-containing material. Using the plasma effluents, anetch rate selectivity of silicon-and-nitrogen-containing material tosilicon over thirty may be achieved. The ion suppressor may be used toprovide a reactive gas having a higher concentration of radicals thanions. Because most of the charged particles of a plasma are filtered orremoved by the ion suppressor, the substrate is not necessarily biasedduring the etch process. Such a process using radicals and other neutralspecies can reduce plasma damage compared to conventional plasma etchprocesses that include sputtering and bombardment. Embodiments of thepresent invention are also advantageous over conventional wet etchprocesses where surface tension of liquids can cause bending and peelingof small features.

In order to better understand and appreciate the invention, reference isnow made to FIG. 1 which is a flow chart of a silicon nitride selectiveetch process according to disclosed embodiments. Silicon nitride is anexample of a silicon-and-nitrogen-containing material. Prior to thefirst operation, a structure is formed in a patterned substrate. Thestructure possesses separate exposed regions of silicon nitride andsilicon. The substrate is then delivered into a processing region(operation 110).

A flow of nitrogen trifluoride is introduced into a plasma regionseparate from the processing region (operation 120). Other sources offluorine may be used to augment or replace the nitrogen trifluoride. Ingeneral, a fluorine-containing precursor may be flowed into the plasmaregion and the fluorine-containing precursor comprises at least oneprecursor selected from the group consisting of atomic fluorine,diatomic fluorine, bromine trifluoride, chlorine trifluoride, nitrogentrifluoride, hydrogen fluoride, sulfur hexafluoride and xenondifluoride. Even carbon containing precursors, such as carbontetrafluoride, trifluoromethane, difluoromethane, fluoromethane and thelike, can be added to the group already listed. The use ofcarbon-containing precursor generally requires an increased flow of theoxygen-containing precursors described herein to react with the carbonbefore it can be incorporated into the substrate. The separate plasmaregion may be referred to as a remote plasma region herein and may bewithin a distinct module from the processing chamber or a compartmentwithin the processing chamber. Oxygen (O₂) is also flowed into theplasma region (operation 125) where it is simultaneously excited in aplasma along with the nitrogen trifluoride. Generally speaking, anoxygen-containing precursor may be flowed into the plasma region and theoxygen-containing precursor may comprise at least one precursor selectedfrom O₂, O₃, N₂O, NO, NO₂, or the like. Some oxygen-containingprecursors may be more reactive than others. Ozone may result in someoxidation of the silicon-and-nitrogen-containing material which couldreduce the selectivities described below.

The plasma effluents formed in the remote plasma region are then flowedinto the substrate processing region (operation 130). The patternedsubstrate is selectively etched (operation 135) such that the exposedsilicon nitride is removed at a rate at least ten times greater than theexposed silicon. The invention involves maintenance of a high atomicflow ratio of oxygen (O) to fluorine (F) in order achieve high etchselectivity of silicon-and-nitrogen-containing films (in this casesilicon nitride). The presence of oxygen helps to oxidize any exposedsilicon rendering silicon domains essentially unetchable by thefluorine-containing plasma effluents in embodiments. In one embodiment,a gas flow ratio (O₂:NF₃) greater than or about 10:1, or in generalterms, greater than or about an atomic flow ratio of between 20:3, wasfound to achieve etch selectivity (silicon nitride:silicon) of greaterthan or about 10:1. In other embodiments, the atomic flow ratio (O:F)may be greater than or about 10:1, for example, by supplying a gas flowratio (O₂:NF₃) of greater than or about 15:1. The etch selectivity(silicon nitride:silicon) may also be greater than or about 15:1,greater than or about 15:1, greater than or about 20:1 or greater thanor about 25:1 in disclosed embodiments. Regions of exposed silicon oxidemay also be present on the patterned substrate. The etch selectivity maybe greater than or about 30:1, greater than or about 50:1 or greaterthan or about 80:1 in disclosed embodiments. Higher ranges may be usedfor fluorine-containing precursors which contain carbon. Additionaloxygen helps to remove the carbon before it can be incorporated in thesubstrate, where it may adversely impact device performance. The moregeneral atomic flow ratio, O:F, is calculated from the gas flow rate ofeach precursor gas and the total number of each atom per molecule. Inthe embodiment wherein one precursor is O₂ and another is NF₃, eachmolecule of oxygen includes two oxygen atoms whereas each molecule ofnitrogen trifluoride includes three fluorine atoms. Using mass flowcontrollers to maintain a gas flow ratio above, e.g. 10:1, will resultin an atomic flow ratio of above 20:3. In another embodiment, theprecursor gases include at least one gas which contains both oxygen andfluorine. The atomic flow rate of all contributions are included whencalculating the atomic flow ratio.

The reactive chemical species are removed from the substrate processingregion and then the substrate is removed from the processing region(operation 145). The flow of oxygen (O₂) into the plasma and resultingflow of oxygen-containing excited species into the substrate processingregion enables the fluorine-containing excited species in the plasmaeffluents to remove the silicon nitride while limiting the removal rateof the exposed silicon. The flow of oxygen-containing excited speciesinto the substrate processing region has little effect on the exposedregions of silicon oxide and the fluorine-containing excited species aresubstantially unable to etch the silicon oxide regions.

Using the oxygen-containing precursor, as described herein, does notsignificantly affect the etch rate of the silicon nitride but doesdecrease the etch rate of silicon, leading to the relatively highselectivity. The fluorine-containing precursor and/or theoxygen-containing precursor may further include one or more relativelyinert gases such as He, N₂, Ar, or the like. The inert gas can be usedto improve plasma stability. Flow rates and ratios of the differentgases may be used to control etch rates and etch selectivity. In anembodiment, the fluorine-containing gas includes NF₃ at a flow rate ofbetween about 5 sccm (standard cubic centimeters per minute) and 300sccm, O₂ at a flow rate of between about 50 sccm and 2 slm (standardliters per minute), He at a flow rate of between about 0 sccm and 3000sccm, and Ar at a flow rate of between about 0 sccm and 3000 sccm. Oneof ordinary skill in the art would recognize that other gases and/orflows may be used depending on a number of factors including processingchamber configuration, substrate size, geometry and layout of featuresbeing etched, and the like. Some hydrogen-containing precursors may alsobe combined with the other precursors or flowed separately into theplasma region, however, the concentration should be kept low. Hydrogenmay interact with the fluorine-containing precursor in the plasma toform precursors which remove silicon oxide by forming solid residueby-products on the oxide surface. This reaction reduces the selectivityof the exposed silicon nitride regions as compared with exposed siliconoxide regions. Though some hydrogen may be useful to introduce in someembodiments, there may also be no or essentially no flow of hydrogeninto the plasma region during the etch process in other embodiments.

The method also includes applying energy to the fluorine-containingprecursor and the oxygen-containing precursor while they are in theremote plasma region to generate the plasma effluents. As would beappreciated by one of ordinary skill in the art, the plasma may includea number of charged and neutral species including radicals and ions. Theplasma may be generated using known techniques (e.g., RF, capacitivelycoupled, inductively coupled, and the like). In an embodiment, theenergy is applied using a capacitively-coupled plasma unit at a sourcepower of between about 10 W and 2000 W and a pressure of between about0.2 Torr and 30 Torr. The capacitively-coupled plasma unit may bedisposed remote from a gas reaction region of the processing chamber.For example, the capacitively-coupled plasma unit and the plasmageneration region may be separated from the gas reaction region by anion suppressor.

Without wishing to bind the coverage of the claims to theoreticalmechanisms which may or may not be entirely correct, some discussion ofpossible mechanisms may prove beneficial. Without the assistance ofradical-oxygen, radical-fluorine is selective towards silicon andsilicon-and-nitrogen-containing material, while leaving silicon oxideessentially unetched. In this invention, radical-fluorine andradical-oxygen are concurrently produced by delivering afluorine-containing precursor and an oxygen-containing precursor intothe remote plasma region. Applicants suppose that a concentration ofradical-fluorine fragments, fluorine ions and atoms are produced anddelivered into the substrate processing region. Applicants furthersuppose that radical-oxygen species are concurrently delivered to thesubstrate processing region. The preponderance of radical-oxygen speciesmay react with exposed silicon regions in the near surface region tocreate a thin silicon oxide layer so exposed region of silicon behavesimilarly to exposed regions of silicon oxide. The thin silicon oxidelayer protects the silicon region from radical fluorine species. As aconsequence, the etching methods outlined herein achieve selectivitytoward silicon-and-nitrogen-containing material.

Blanket wafers of silicon oxide, silicon and silicon nitride were usedto quantify the etch rates for an exemplary process. A remote plasma wasformed from nitrogen trifluoride, oxygen (O₂), helium and argon and theeffluents etched blanket wafers of each of the three films in separateprocesses. The etch process removed silicon nitride at about one hundredtimes the rate of silicon oxide and over thirty times the rate ofsilicon in the form of polysilicon. The selectivity, the non-localplasma, the controlled ionic concentration and the lack of solidbyproducts, each make these etch processes well suited for removing ortrimming delicate silicon-and-nitrogen-containing material structureswith little deformation and while removing little or no silicon oxide.These selectivities also apply generally tosilicon-and-nitrogen-containing material and to silicon nitride inparticular.

The temperature of the substrate may be between about −30° C. and about150° C. in general. The etch rate has been found to be higher for thelower temperatures within this range. In embodiments, the temperature ofthe substrate during the etches described herein is about −20° C., 0° C.or more, about 5° C. or more or about 10° C. or more. The substratetemperatures may be less than or about 150° C., less than or about 100°C., less than or about 50° C., less than or about 30° C., less than orabout 20° C., less than or about 15° C. or less than or about 10° C. indifferent embodiments. The data further show an increase in etch rate asa function of process pressure. The pressure within the substrateprocessing region is below or about 50 Torr, below or about 30 Torr,below or about 20 Torr, below or about 10 Torr or below or about 5 Torr.The pressure may be above or about 0.1 Torr, above or about 0.2 Torr,above or about 0.5 Torr or above or about 1 Torr in embodiments of theinvention. Any of the upper limits on temperature or pressure may becombined with lower limits to form additional embodiments. Generallyspeaking, the processes described herein may be used to describe filmswhich contain silicon and nitrogen (and not just silicon nitride). Theremote plasma etch processes may remove silicon-and-nitrogen-containingmaterial which includes an atomic concentration of about 30% or moresilicon and about 30% or more nitrogen in embodiments of the invention.The silicon-and-nitrogen-containing material may also consistessentially of silicon and nitrogen, allowing for small dopantconcentrations and other undesirable or desirable minority additives. Ofcourse, the silicon-and-nitrogen-containing material may consistessentially of silicon nitride in embodiments of the invention.

Additional process parameters are disclosed in the course of describingan exemplary processing chamber and system.

Exemplary Processing System

Processing chambers that may implement embodiments of the presentinvention may be included within processing platforms such as theCENTURA® and PRODUCER® systems, available from Applied Materials, Inc.of Santa Clara, Calif. Examples of substrate processing chambers thatcan be used with exemplary methods of the invention may include thoseshown and described in co-assigned U.S. Provisional Patent App. No.60/803,499 to Lubomirsky et al, filed May 30, 2006, and titled “PROCESSCHAMBER FOR DIELECTRIC GAPFILL,” the entire contents of which is hereinincorporated by reference for all purposes. Additional exemplary systemsmay include those shown and described in U.S. Pat. Nos. 6,387,207 and6,830,624, which are also incorporated herein by reference for allpurposes.

FIG. 2A is a substrate processing chamber 200 according to disclosedembodiments. A remote plasma system 210 may process thefluorine-containing precursor which then travels through a gas inletassembly 211. Two distinct gas supply channels are visible within thegas inlet assembly 211. A first channel 212 carries a gas that passesthrough the remote plasma system 210 (RPS), while a second channel 213bypasses the remote plasma system 210. Either channel may be used forthe fluorine-containing precursor, in embodiments. On the other hand,the first channel 212 may be used for the process gas and the secondchannel 213 may be used for a treatment gas. The lid (or conductive topportion) 221 and a perforated partition 253 are shown with an insulatingring 224 in between, which allows an AC potential to be applied to thelid 221 relative to perforated partition 253. The AC potential strikes aplasma in chamber plasma region 220. The process gas may travel throughfirst channel 212 into chamber plasma region 220 and may be excited by aplasma in chamber plasma region 220 alone or in combination with remoteplasma system 210. If the process gas (the fluorine-containingprecursor) flows through second channel 213, then only the chamberplasma region 220 is used for excitation. The combination of chamberplasma region 220 and/or remote plasma system 210 may be referred to asa remote plasma system herein. The perforated partition (also referredto as a showerhead) 253 separates chamber plasma region 220 from asubstrate processing region 270 beneath showerhead 253. Showerhead 253allows a plasma present in chamber plasma region 220 to avoid directlyexciting gases in substrate processing region 270, while still allowingexcited species to travel from chamber plasma region 220 into substrateprocessing region 270.

Showerhead 253 is positioned between chamber plasma region 220 andsubstrate processing region 270 and allows plasma effluents (excitedderivatives of precursors or other gases) created within remote plasmasystem 210 and/or chamber plasma region 220 to pass through a pluralityof through-holes 256 that traverse the thickness of the plate. Theshowerhead 253 also has one or more hollow volumes 251 which can befilled with a precursor in the form of a vapor or gas (such as asilicon-containing precursor) and pass through small holes 255 intosubstrate processing region 270 but not directly into chamber plasmaregion 220. Showerhead 253 is thicker than the length of the smallestdiameter 250 of the through-holes 256 in this disclosed embodiment. Inorder to maintain a significant concentration of excited speciespenetrating from chamber plasma region 220 to substrate processingregion 270, the length 226 of the smallest diameter 250 of thethrough-holes may be restricted by forming larger diameter portions ofthrough-holes 256 part way through the showerhead 253. The length of thesmallest diameter 250 of the through-holes 256 may be the same order ofmagnitude as the smallest diameter of the through-holes 256 or less indisclosed embodiments.

Showerhead 253 may be configured to serve the purpose of an ionsuppressor as shown in FIG. 2A. Alternatively, a separate processingchamber element may be included (not shown) which suppresses the ionconcentration traveling into substrate processing region 270. Lid 221and showerhead 253 may function as a first electrode and secondelectrode, respectively, so that lid 221 and showerhead 253 may receivedifferent electric voltages. In these configurations, electrical power(e.g., RF power) may be applied to lid 221, showerhead 253, or both. Forexample, electrical power may be applied to lid 221 while showerhead 253(serving as ion suppressor) is grounded. The substrate processing systemmay include a RF generator that provides electrical power to the lidand/or showerhead 253. The voltage applied to lid 221 may facilitate auniform distribution of plasma (i.e., reduce localized plasma) withinchamber plasma region 220. To enable the formation of a plasma inchamber plasma region 220, insulating ring 224 may electrically insulatelid 221 from showerhead 253. Insulating ring 224 may be made from aceramic and may have a high breakdown voltage to avoid sparking.Portions of substrate processing chamber 200 near thecapacitively-coupled plasma components just described may furtherinclude a cooling unit (not shown) that includes one or more coolingfluid channels to cool surfaces exposed to the plasma with a circulatingcoolant (e.g., water).

In the embodiment shown, showerhead 253 may distribute (viathrough-holes 256) process gases which contain oxygen, fluorine and/ornitrogen and/or plasma effluents of such process gases upon excitationby a plasma in chamber plasma region 220. In embodiments, the processgas introduced into the remote plasma system 210 and/or chamber plasmaregion 220 may contain fluorine (e.g. F₂, NF₃ or XeF₂). The process gasmay also include a carrier gas such as helium, argon, nitrogen (N₂),etc. Plasma effluents may include ionized or neutral derivatives of theprocess gas and may also be referred to herein as radical-fluorinereferring to the atomic constituent of the process gas introduced.

Through-holes 256 are configured to suppress the migration ofionically-charged species out of the chamber plasma region 220 whileallowing uncharged neutral or radical species to pass through showerhead253 into substrate processing region 270. These uncharged species mayinclude highly reactive species that are transported with less-reactivecarrier gas by through-holes 256. As noted above, the migration of ionicspecies by through-holes 256 may be reduced, and in some instancescompletely suppressed. Controlling the amount of ionic species passingthrough showerhead 253 provides increased control over the gas mixturebrought into contact with the underlying wafer substrate, which in turnincreases control of the deposition and/or etch characteristics of thegas mixture. For example, adjustments in the ion concentration of thegas mixture can significantly alter its etch selectivity (e.g., siliconnitride:silicon etch ratios).

In embodiments, the number of through-holes 256 may be between about 60and about 2000. Through-holes 256 may have a variety of shapes but aremost easily made round. The smallest diameter 250 of through-holes 256may be between about 0.5 mm and about 20 mm or between about 1 mm andabout 6 mm in disclosed embodiments. There is also latitude in choosingthe cross-sectional shape of through-holes, which may be made conical,cylindrical or combinations of the two shapes. The number of small holes255 used to introduce unexcited precursors into substrate processingregion 270 may be between about 100 and about 5000 or between about 500and about 2000 in different embodiments. The diameter of the small holes255 may be between about 0.1 mm and about 2 mm.

Through-holes 256 may be configured to control the passage of theplasma-activated gas (i.e., the ionic, radical, and/or neutral species)through showerhead 253. For example, the aspect ratio of the holes(i.e., the hole diameter to length) and/or the geometry of the holes maybe controlled so that the flow of ionically-charged species in theactivated gas passing through showerhead 253 is reduced. Through-holes256 in showerhead 253 may include a tapered portion that faces chamberplasma region 220, and a cylindrical portion that faces substrateprocessing region 270. The cylindrical portion may be proportioned anddimensioned to control the flow of ionic species passing into substrateprocessing region 270. An adjustable electrical bias may also be appliedto showerhead 253 as an additional means to control the flow of ionicspecies through showerhead 253.

Alternatively, through-holes 256 may have a smaller inner diameter (ID)toward the top surface of showerhead 253 and a larger ID toward thebottom surface. In addition, the bottom edge of through-holes 256 may bechamfered to help evenly distribute the plasma effluents in substrateprocessing region 270 as the plasma effluents exit the showerhead andthereby promote even distribution of the plasma effluents and precursorgases. The smaller ID may be placed at a variety of locations alongthrough-holes 256 and still allow showerhead 253 to reduce the iondensity within substrate processing region 270. The reduction in iondensity results from an increase in the number of collisions with wallsprior to entry into substrate processing region 270. Each collisionincreases the probability that an ion is neutralized by the acquisitionor loss of an electron from the wall. Generally speaking, the smaller IDof through-holes 256 may be between about 0.2 mm and about 20 mm. Inother embodiments, the smaller ID may be between about 1 mm and 6 mm orbetween about 0.2 mm and about 5 mm. Further, aspect ratios of thethrough-holes 256 (i.e., the smaller ID to hole length) may beapproximately 1 to 20. The smaller ID of the through-holes may be theminimum ID found along the length of the through-holes. The crosssectional shape of through-holes 256 may be generally cylindrical,conical, or any combination thereof.

FIG. 2B is a bottom view of a showerhead 253 for use with a processingchamber according to disclosed embodiments. Showerhead 253 correspondswith the showerhead shown in FIG. 2A. Through-holes 256 are depictedwith a larger inner-diameter (ID) on the bottom of showerhead 253 and asmaller ID at the top. Small holes 255 are distributed substantiallyevenly over the surface of the showerhead, even amongst thethrough-holes 256 which helps to provide more even mixing than otherembodiments described herein.

An exemplary patterned substrate may be supported by a pedestal (notshown) within substrate processing region 270 when fluorine-containingplasma effluents and oxygen-containing plasma effluents arrive throughthrough-holes 256 in showerhead 253. Though substrate processing region270 may be equipped to support a plasma for other processes such ascuring, no plasma is present during the etching of patterned substrate,in embodiments of the invention.

A plasma may be ignited either in chamber plasma region 220 aboveshowerhead 253 or substrate processing region 270 below showerhead 253.A plasma is present in chamber plasma region 220 to produce theradical-fluorine from an inflow of the fluorine-containing precursor. AnAC voltage typically in the radio frequency (RF) range is appliedbetween the conductive top portion (lid 221) of the processing chamberand showerhead 253 to ignite a plasma in chamber plasma region 220during deposition. An RF power supply generates a high RF frequency of13.56 MHz but may also generate other frequencies alone or incombination with the 13.56 MHz frequency.

The top plasma may be left at low or no power when the bottom plasma inthe substrate processing region 270 is turned on to either cure a filmor clean the interior surfaces bordering substrate processing region270. A plasma in substrate processing region 270 is ignited by applyingan AC voltage between showerhead 253 and the pedestal or bottom of thechamber. A cleaning gas may be introduced into substrate processingregion 270 while the plasma is present.

The pedestal may have a heat exchange channel through which a heatexchange fluid flows to control the temperature of the substrate. Thisconfiguration allows the substrate temperature to be cooled or heated tomaintain relatively low temperatures (from room temperature throughabout 120° C.). The heat exchange fluid may comprise ethylene glycol andwater. The wafer support platter of the pedestal (preferably aluminum,ceramic, or a combination thereof) may also be resistively heated inorder to achieve relatively high temperatures (from about 120° C.through about 1100° C.) using an embedded single-loop embedded heaterelement configured to make two full turns in the form of parallelconcentric circles. An outer portion of the heater element may runadjacent to a perimeter of the support platter, while an inner portionruns on the path of a concentric circle having a smaller radius. Thewiring to the heater element passes through the stem of the pedestal.

The chamber plasma region or a region in a remote plasma system may bereferred to as a remote plasma region. In embodiments, the radicalprecursors (e.g. radical-fluorine and radical-oxygen) are formed in theremote plasma region and travel into the substrate processing regionwhere the combination preferentially etchessilicon-and-nitrogen-containing material. Plasma power may essentiallybe applied only to the remote plasma region, in embodiments, to ensurethat the radical-fluorine and the radical-oxygen (which together may bereferred to as plasma effluents) are not further excited in thesubstrate processing region.

In embodiments employing a chamber plasma region, the excited plasmaeffluents are generated in a section of the substrate processing regionpartitioned from a deposition region. The deposition region, also knownherein as the substrate processing region, is where the plasma effluentsmix and react to etch the patterned substrate (e.g., a semiconductorwafer). The excited plasma effluents may also be accompanied by inertgases (in the exemplary case, argon). The substrate processing regionmay be described herein as “plasma-free” during the etch of thepatterned substrate. “Plasma-free” does not necessarily mean the regionis devoid of plasma. A relatively low concentration of ionized speciesand free electrons created within the plasma region do travel throughpores (apertures) in the partition (showerhead/ion suppressor) due tothe shapes and sizes of through-holes 256. In some embodiments, there isessentially no concentration of ionized species and free electronswithin the substrate processing region. The borders of the plasma in thechamber plasma region are hard to define and may encroach upon thesubstrate processing region through the apertures in the showerhead. Inthe case of an inductively-coupled plasma, a small amount of ionizationmay be effected within the substrate processing region directly.Furthermore, a low intensity plasma may be created in the substrateprocessing region without eliminating desirable features of the formingfilm. All causes for a plasma having much lower intensity ion densitythan the chamber plasma region (or a remote plasma region, for thatmatter) during the creation of the excited plasma effluents do notdeviate from the scope of “plasma-free” as used herein.

Nitrogen trifluoride (or another fluorine-containing precursor) may beflowed into chamber plasma region 220 at rates between about 5 sccm andabout 500 sccm, between about 10 sccm and about 300 sccm, between about25 sccm and about 200 sccm, between about 50 sccm and about 150 sccm orbetween about 75 sccm and about 125 sccm in different embodiments.Oxygen (O₂) may be flowed into chamber plasma region 220 at ratesgreater than or about 250 sccm, greater than or about 500 sccm, greaterthan or about 1 slm, greater than or about 2 slm or greater than orabout 5 slm in different embodiments.

Combined flow rates of fluorine-containing precursor andoxygen-containing precursor into the chamber may account for 0.05% toabout 20% by volume of the overall gas mixture; the remainder beingcarrier gases. The fluorine-containing precursor and theoxygen-containing precursor are flowed into the remote plasma region butthe plasma effluents have the same volumetric flow ratio, inembodiments. In the case of the fluorine-containing precursor, a purgeor carrier gas may be first initiated into the remote plasma regionbefore those of the fluorine-containing gas to stabilize the pressurewithin the remote plasma region.

Plasma power applied to the remote plasma region can be a variety offrequencies or a combination of multiple frequencies. In the exemplaryprocessing system the plasma is provided by RF power delivered betweenlid 221 and showerhead 253. The RF power may be between about 10 Wattsand about 15000 Watts, between about 10 Watts and about 5000 Watts,between about 10 Watts and about 2000 Watts, between about 20 Watts andabout 1500 Watts or between about 50 Watts and about 500 Watts indifferent embodiments. The RF frequency applied in the exemplaryprocessing system may be low RF frequencies less than about 200 kHz,high RF frequencies between about 10 MHz and about 15 MHz or microwavefrequencies greater than or about 1 GHz in different embodiments.

Substrate processing region 270 can be maintained at a variety ofpressures during the flow of carrier gases and plasma effluents intosubstrate processing region 270. The pressure within the substrateprocessing region is below or about 50 Torr, below or about 30 Torr,below or about 20 Torr, below or about 10 Torr or below or about 5 Torr.The pressure may be above or about 0.1 Torr, above or about 0.2 Torr,above or about 0.5 Torr or above or about 1 Torr in embodiments of theinvention. Lower limits on the pressure may be combined with upperlimits on the pressure to arrive at further embodiments of theinvention.

In one or more embodiments, the substrate processing chamber 200 can beintegrated into a variety of multi-processing platforms, including theProducer™ GT, Centura™ AP and Endura™ platforms available from AppliedMaterials, Inc. located in Santa Clara, Calif. Such a processingplatform is capable of performing several processing operations withoutbreaking vacuum. Processing chambers that may implement embodiments ofthe present invention may include dielectric etch chambers or a varietyof chemical vapor deposition chambers, among other types of chambers.

Embodiments of the deposition systems may be incorporated into largerfabrication systems for producing integrated circuit chips. FIG. 3 showsone such system 300 of deposition, baking and curing chambers accordingto disclosed embodiments. In the figure, a pair of FOUPs (front openingunified pods) 302 supply substrate substrates (e.g., 300 mm diameterwafers) that are received by robotic arms 304 and placed into a lowpressure holding areas 306 before being placed into one of the waferprocessing chambers 308 a-f. A second robotic arm 310 may be used totransport the substrate wafers from the low pressure holding areas 306to the wafer processing chambers 308 a-f and back. Each wafer processingchamber 308 a-f, can be outfitted to perform a number of substrateprocessing operations including the dry etch processes described hereinin addition to cyclical layer deposition (CLD), atomic layer deposition(ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD),etch, pre-clean, degas, orientation and other substrate processes.

The wafer processing chambers 308 a-f may include one or more systemcomponents for depositing, annealing, curing and/or etching a flowabledielectric film on the substrate wafer. In one configuration, two pairsof the processing chamber (e.g., 308 c-d and 308 e-f) may be used todeposit dielectric material on the substrate, and the third pair ofprocessing chambers (e.g., 308 a-b) may be used to etch the depositeddielectric. In another configuration, all three pairs of chambers (e.g.,308 a-f) may be configured to etch a dielectric film on the substrate.Any one or more of the processes described may be carried out onchamber(s) separated from the fabrication system shown in differentembodiments.

The substrate processing system is controlled by a system controller. Inan exemplary embodiment, the system controller includes a hard diskdrive, a floppy disk drive and a processor. The processor contains asingle-board computer (SBC), analog and digital input/output boards,interface boards and stepper motor controller boards. Various parts ofCVD system conform to the Versa Modular European (VME) standard whichdefines board, card cage, and connector dimensions and types. The VMEstandard also defines the bus structure as having a 16-bit data bus anda 24-bit address bus.

System controller 357 is used to control motors, valves, flowcontrollers, power supplies and other functions required to carry outprocess recipes described herein. A gas handling system 355 may also becontrolled by system controller 357 to introduce gases to one or all ofthe wafer processing chambers 308 a-f. System controller 357 may rely onfeedback from optical sensors to determine and adjust the position ofmovable mechanical assemblies in gas handling system 355 and/or in waferprocessing chambers 308 a-f. Mechanical assemblies may include therobot, throttle valves and susceptors which are moved by motors underthe control of system controller 357.

In an exemplary embodiment, system controller 357 includes a hard diskdrive (memory), USB ports, a floppy disk drive and a processor. Systemcontroller 357 includes analog and digital input/output boards,interface boards and stepper motor controller boards. Various parts ofmulti-chamber processing system 300 which contains substrate processingchamber 200 are controlled by system controller 357. The systemcontroller executes system control software in the form of a computerprogram stored on computer-readable medium such as a hard disk, a floppydisk or a flash memory thumb drive. Other types of memory can also beused. The computer program includes sets of instructions that dictatethe timing, mixture of gases, chamber pressure, chamber temperature, RFpower levels, susceptor position, and other parameters of a particularprocess.

A process for etching, depositing or otherwise processing a film on asubstrate or a process for cleaning chamber can be implemented using acomputer program product that is executed by the controller. Thecomputer program code can be written in any conventional computerreadable programming language: for example, 68000 assembly language, C,C++, Pascal, Fortran or others. Suitable program code is entered into asingle file, or multiple files, using a conventional text editor, andstored or embodied in a computer usable medium, such as a memory systemof the computer. If the entered code text is in a high level language,the code is compiled, and the resultant compiler code is then linkedwith an object code of precompiled Microsoft Windows® library routines.To execute the linked, compiled object code the system user invokes theobject code, causing the computer system to load the code in memory. TheCPU then reads and executes the code to perform the tasks identified inthe program.

The interface between a user and the controller may be via atouch-sensitive monitor and may also include a mouse and keyboard. Inone embodiment two monitors are used, one mounted in the clean room wallfor the operators and the other behind the wall for the servicetechnicians. The two monitors may simultaneously display the sameinformation, in which case only one is configured to accept input at atime. To select a particular screen or function, the operator touches adesignated area on the display screen with a finger or the mouse. Thetouched area changes its highlighted color, or a new menu or screen isdisplayed, confirming the operator's selection.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The patterned substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. Exposed “silicon” of the patternedsubstrate is predominantly Si but may include minority concentrations ofother elemental constituents such as nitrogen, oxygen, hydrogen, carbonand the like. Exposed “silicon nitride” of the patterned substrate ispredominantly Si₃N₄ but may include minority concentrations of otherelemental constituents such as oxygen, hydrogen, carbon and the like.Exposed “silicon oxide” of the patterned substrate is predominantly SiO₂but may include minority concentrations of other elemental constituentssuch as nitrogen, hydrogen, carbon and the like. In some embodiments,silicon oxide films etched using the methods disclosed herein consistessentially of silicon and oxygen. The term “precursor” is used to referto any process gas which takes part in a reaction to either removematerial from or deposit material onto a surface. “Plasma effluents”describe gas exiting from the chamber plasma region and entering thesubstrate processing region. Plasma effluents are in an “excited state”wherein at least some of the gas molecules are in vibrationally-excited,dissociated and/or ionized states. A “radical precursor” is used todescribe plasma effluents (a gas in an excited state which is exiting aplasma) which participate in a reaction to either remove material fromor deposit material on a surface. “Radical-fluorine” (or“radical-oxygen”) are radical precursors which contain fluorine (oroxygen) but may contain other elemental constituents. The phrase “inertgas” refers to any gas which does not form chemical bonds when etchingor being incorporated into a film. Exemplary inert gases include noblegases but may include other gases so long as no chemical bonds areformed when (typically) trace amounts are trapped in a film.

The terms “gap” and “trench” are used throughout with no implicationthat the etched geometry has a large horizontal aspect ratio. Viewedfrom above the surface, trenches may appear circular, oval, polygonal,rectangular, or a variety of other shapes. A trench may be in the shapeof a moat around an island of material. The term “via” is used to referto a low aspect ratio trench (as viewed from above) which may or may notbe filled with metal to form a vertical electrical connection. As usedherein, a conformal etch process refers to a generally uniform removalof material on a surface in the same shape as the surface, i.e., thesurface of the etched layer and the pre-etch surface are generallyparallel. A person having ordinary skill in the art will recognize thatthe etched interface likely cannot be 100% conformal and thus the term“generally” allows for acceptable tolerances.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of thedisclosed embodiments. Additionally, a number of well known processesand elements have not been described in order to avoid unnecessarilyobscuring the present invention. Accordingly, the above descriptionshould not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the dielectric material”includes reference to one or more dielectric materials and equivalentsthereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

What is claimed is:
 1. A method of etching a patterned substrate in asubstrate processing region of a substrate processing chamber, whereinthe patterned substrate has an exposed silicon-and-nitrogen-containingregion, the method comprising: flowing each of a fluorine-containingprecursor and an oxygen-containing precursor into a remote plasma regionfluidly coupled to the substrate processing region while forming aplasma in the plasma region to produce plasma effluents; and etching theexposed silicon-and-nitrogen-containing region by flowing the plasmaeffluents into the substrate processing region through through-holes ina showerhead.
 2. The method of claim 1 wherein the exposedsilicon-and-nitrogen-containing region is silicon nitride.
 3. The methodof claim 1 wherein the exposed silicon-and-nitrogen-containing regionconsists essentially of silicon and nitrogen.
 4. The method of claim 1wherein the exposed silicon-and-nitrogen-containing region comprisesabout 30% or more silicon and about 30% or more nitrogen.
 5. The methodof claim 1 wherein a temperature of the patterned substrate is greaterthan or about −20° C. and less than or about 150° C.
 6. The method ofclaim 1 wherein a pressure within the substrate processing region isbelow or about 50 Torr and above or about 0.1 Torr.
 7. The method ofclaim 1 wherein forming a plasma in the plasma region to produce plasmaeffluents comprises applying RF power between about 10 Watts and about15,000 Watts to the plasma region.
 8. The method of claim 1 wherein theplasma is a capacitively-coupled plasma.
 9. The method of claim 1wherein the oxygen-containing precursor comprises molecular oxygen (O₂).10. The method of claim 1 wherein the oxygen-containing precursorcomprises at least one of O₂, O₃, NO, N₂O or NO₂.
 11. The method ofclaim 1 wherein the substrate processing region is plasma-free.
 12. Themethod of claim 1 wherein the patterned substrate further comprises anexposed silicon oxide region and the selectivity of the etchingoperation (exposed silicon-and-nitrogen-containing region:exposedsilicon oxide region) is greater than or about 30:1.
 13. The method ofclaim 1 wherein the patterned substrate further comprises an exposedsilicon region and the selectivity of the etching operation (exposedsilicon-and-carbon-containing region:exposed silicon region) is greaterthan or about 10:1.
 14. The method of claim 1 wherein the patternedsubstrate further comprises an exposed silicon region and theselectivity of the etching operation (exposedsilicon-and-carbon-containing region:exposed silicon region) is greaterthan or about 15:1.
 15. The method of claim 1 wherein thefluorine-containing precursor comprises NF₃.
 16. The method of claim 1wherein the fluorine-containing precursor comprises a precursor selectedfrom the group consisting of hydrogen fluoride, atomic fluorine,diatomic fluorine, nitrogen trifluoride, carbon tetrafluoride and xenondifluoride.
 17. The method of claim 1 wherein the fluorine-containingprecursor and the plasma effluents are essentially devoid of hydrogen.18. The method of claim 1 wherein there is essentially no concentrationof ionized species and free electrons within the substrate processingregion.
 19. The method of claim 1 wherein the minimum ID of thethrough-holes in the showerhead is between about 0.2 mm and about 5 mm.20. The method of claim 1 wherein flowing each of thefluorine-containing precursor and the oxygen-containing precursor intothe remote plasma region comprises maintaining an O:F atomic flow ratioabove or about 0.5:1 and below or about 10:1.